Diabetic Retinopathy: How Does Diabetes Affect the Eyes and Vision

The effects of diabetes on the eye range from errors of refraction and color vision, to cataract and glaucoma, to the devastating diabetic retinopathy and its complications. In this article, we shall discuss largely about the more serious problem of diabetic retinopathy and how does diabetic retinopathy affect the eyes and vision and thereafter dwell on the other effects with emphasis on the role of the physician.

Diabetic Retinopathy:

The Diabetic Retinopathy is a serious condition affecting individuals with diabetes, leading to potential vision loss or blindness if left untreated. The Diabetes Control and Complication Trial has proven the value of good glycemic control in preventing retinopathy and /or delaying its progression. The primary care a physician has a crucial role in translating these results into practice. There must be a close collaboration between primary care physicians and ophthalmologists to care for at-risk patients. To manage diabetic patients in a cost-effective manner, the primary care physician must understand the risk factors for diabetic retinopathy, its pathogenesis and clinical signs, screening methods, and the need to obtain timely ophthalmologic consultation.

Diabetes and Retinopathy Relation:

The risk of developing diabetic retinopathy is directly associated with the duration of the disease.

Type 1 Diabetes:

Type 1 diabetic patients are fewer in number, but they have more frequent and more severe ocular complications. 5 years after onset of diabetes approximately 25% of type 1 patients have some form of retinopathy. After 10 years of having diabetes, more than 70% of these patients have retinopathy. About one third of such patients have macular edema and about one third have proliferative retinopathy, the most vision-threatening form of the disease.

Type 2 Diabetes:

In Type 2 Diabetes, study shows that 37% of the subjects had retinopathy. Up to 3% these patients can have clinically significant macular edema or vision-threatening proliferative disease at the time of the initial diagnosis of diabetes. In Type 2 diabetes, patients with duration of 15 years or more the risk of retinopathy is about 78%. About one-third of such patients have macular edema and about one -sixth have proliferative retinopathy.

Risk Factors in Diabetic Retinopathy:

There are some common factors that may contribute to the development and progression of diabetic retinopathy. Here are the common factors:

Proteinuria: Proteinuria due to diabetic nephropathy has been shown to be a risk factor for the incidence of diabetic retinopathy. Recognition of proteinuria as a risk factor has important implications for the primary care physician who thus has a simple marker for identifying diabetic patients at risk and ensuring that they have appropriate eye examinations.
Cigarette Smoking and Blood Pressure: Cigarette smoking and high blood pressure are particularly amenable to intervention by the primary care of physician. High blood pressure is significantly associated with both the development and progression of diabetic retinopathy.
Pregnancy: Pregnancy is a risk factor for the progression of diabetic retinopathy. Of patients with mild NPDR at the onset of pregnancy, almost one half progresses to more severe NPDR during the pregnancy, and approximately 5% progresses to diabetic retinopathy. Women with gestational diabetes have no increased risk of developing diabetic retinopathy during pregnancy.

Diagnosis of Diabetic Retinopathy:

Examination of the retina requires the pupil to be dilated. This is done by instilling mydriatic drops two to three times and waiting for about 30 minutes.

A Direct Ophthalmoscope can be used as a screening tool to evaluate the fundus. Though it provides a magnified view of the retina, the view is two-dimensional. Macular edema and early neovascularization cannot be adequately evaluated. Also, the field of view is so narrow that neovascularization outside the most posterior aspects of the fundus can be missed.

Indirect Ophthalmoscopy is an excellent screening method for evaluating a large area of the fundus three-dimensionally. A panoramic view facilitates the evaluation of the equator and periphery of the retina.

Indirect Biomicroscopy on a slit lamp with 90D lens provides three-dimensional viewing of the fundus with excellent magnification that allows evaluation of macular edema and movascularization over a wide field.

Both Indirect Ophthalmoscopy and BIomicroscopy require experience and skill and are best performed by retina specialists.

Treatment of Diabetic Retinopathy:

1. Macular Edema: Macular Edema is the most frequent cause of visual loss in eyes with a background of diabetic retinopathy and is present in 10% of all diabetic patients. Study shows that a 50% reduction in visual loss in eyes with clinically significant edema treated with focal argon laser photocoagulation.

2. Proliferative Diabetic Retinopathy: The Diabetic Retinopathy Study shows that scatter or panretinal laser photocoagulation (PRP) causes regression of proliferative diabetic retinopathy and reduces the rate of severe visual loss by 60%. In treating proliferative diabetic retinopathy, 1550 laser burns are initially scattered in the entire peripheral retina outside the macula in 3 settings. The goal of panretinal photocoagulation is to cause regression of existing neovascular tissue and to prevent new vessel formation in the future.

3. Vitreous Hemorrhage: The Diabetic Retinopathy Vitrectomy Study (DRVS), shows that eyes with recent severe vitreous hemorrhages have a greater chance of prompt recovery of visual acuity when treated by early vitrectomy.

It must be clearly understood that although these treatments are very successful in reducing further visual loss, they do not cure or reverse Diabetic Retinopathy. In few patients retinopathy may progress despite a physician’s best efforts.

The physician must also bear in mind that laser treatment is essentially a non-invasive outdoor procedure and does not require the blood sugar to be controlled. Hence, laser treatment should by no means be delayed.

Medical Management of Diabetic Retinopathy:

There is no doubt that laser photocoagulation is the treatment of choice for macular edema and proliferative diabetic retinopathy. However, the role of smoking, hypertension, hyperlipidemia in the progression of retinopathy should be considered.

The Primary Care of Physician:

The primary care of physician plays a key role not only in the prevention of diabetic retinopathy, but also in its management.

Screening and Surveillance:

Ophthalmoscopic examination with dilation misses at least 20% of cases of advanced retinopathy, whereas ophthalmoscopy without dilation misses even ore cases and is not recommended. When dilated ophthalmoscopic examination is done, the best results are obtained by an ophthalmologist.

Recommended Guidelines:

Dialed fundus examination at diagnosis for all diabetic patients by an Ophthalmologist.
Annual check up for patients with no retinopathy or slowly progressive retinopathy.
More frequent examinations in case of: 1 Progressive retinopathy, 2 Higher level of the glycated hemoglobin, 3 Gross proteinuria/poor glycemic control, 4 After institution of intensive treatment in patients who have had a long history of poor diabetic control.
Diabetic with pregnancy – Fundus examination at 1st trimester and thereafter once every trimester or more frequently, if required.
Patients with macular edema, severe NPDR, Proliferative Retinopathy require prompt care of an experienced Ophthalmologist/Retina Specialist. Laser treatment at this stage is associated with 50% reduction in the risk of severe visual loss.

How does diabetic affect eyes and vision:

High blood sugar levels over an extended period are the primary cause of diabetic retinopathy. The excess sugar weakens and damages the tiny blood vessels nourishing the retina.

Effects of Diabetic Retinopathy and Treatment:

1. Cataract:

Cataracts occur at an earlier age and progress more rapidly in a diabetic patient. It not only hinders the vision of the diabetic patient, but also hinders visualization of the retina by the Ophthalmologist. It could make laser treatment difficult. At times, a cataract removal may be recommended more to facilitate laser than for visual improvement.

At present, the most advanced method of cataract surgery is Phacoemulsification. This technique uses a needle powered with ultrasonic energy to fragment the cataract and sucks it out through a 2.8 mm incision.

The surgery is performed under local anaesthesia with particularly no prior fasting. Hence, the patient is not required to alter his diet or medications. As in any other surgery, it is desirable to have the patient’s blood sugar under control. However, in a diabetic patient a fasting sugar of <140 mg/dl or PP sugar of <200 is quite acceptable.

2. Glaucoma:

A higher prevalence of Glaucoma is seen in diabetic population. It has been postulated that a diabetic patient is at an increased risk of optic nerve damage owing to vascular factors. Because diabetic patients may be at an increased risk of glaucoma, measurement of intraocular pressure and ophthalmoscopic examination of cup: disc ratio is an important part of ophthalmologic examination.

Rubeotic (Neovascular) is seen in eyes with severe ischemia and advanced proliferative changes. This could often result in a painful blind eye. Ablative methods like cyclocryo are resorted to in such situations to relieve the patients of pain.

3. Errors of Refraction:

A sudden change in vision, especially in children and young diabetics is due to a change in the refractive media. Reversible osmotic swelling of the lens due to rapid changes in blood sugar has been postulated to be responsible for this. Hence, it is recommended that prescription of glasses may be deferred for some time if the blood sugar is going through large fluctuations.

4. Color Vision:

disturbances in color vision in the diabetics are known to occur even before the development of retinopathy. Maculopathy only worsens things. Patients on self-monitoring may have difficulty in interpreting results where color matching is required. Meters with digital displays should be considered.

Prevention and Management of Diabetic Retinopathy:

1. Controlling Blood Sugar:

It is essential to keep blood sugar levels under control and within normal ranges to avoid diabetic retinopathy from developing or worsening. The patients with high blood sugar have the risk of development and progression diabetic retinopathy.

2. Routine Eye-checkups:

A person with diabetic needs regular ocular examinations. This will help in the early identification and prompt management of retinopathy. Especially, the individuals who are having the high blood pressure and high blood sugar need to visit the healthcare professional on regular basis.

3. Blood Pressure Management:

Keeping blood pressure under control can significantly reduce the risk and progression of diabetic retinopathy. Elevated blood pressure can impact on optic nerve which plays a crucial role in transmitting signals from the retina to the brain. Hypertension may cause the optic nerve to swell, a condition called hypertensive optic neuropathy. This swelling can further contribute to vision problems.

Conclusion:

Diabetic retinopathy is a severe condition that demands attention, especially for individuals with diabetics. There is a need for a concerted effort from all concerned to educate every diabetic patient about the devasting effects the disease might have on their vision and guide them to an Ophthalmologist-preferably a Retina Specialist.